Alligatorweed (Alternanthera philoxeroides) is an invasive plant. It is a native of Argentina and was first detected in North Carolina in 1967.

Alligator weed is an emergent or rooted floating plant that invades aquatic areas and adjoining uplands throughout the southern portion of the United States. Growth can reduce water flow and quality, leading to fish mortality as well as increased mosquito presence. Several species of insects have been released for biological control of alligator weed.